Angled bus bar

ABSTRACT

This disclosure provides configurations, methods of use, and methods of fabrication for a bus bar of an optically switchable device. In one aspect, an apparatus includes a substrate and an optically switchable device disposed on a surface of the substrate. The optically switchable device has a perimeter with at least one corner including a first side, a second side, and a first vertex joining the first side and the second side. A first bus bar and a second bus bar are affixed to the optically switchable device and configured to deliver current and/or voltage for driving switching of the device. The first bus bar is proximate to the corner and includes a first arm and a second arm having a configuration that substantially follows the shape of the first side, the first vertex, and the second side of the corner.

CROSS REFERENCE TO RELATED APPLICATION

An Application Data Sheet is filed concurrently with this specificationas part of the present application. Each application that the presentapplication claims benefit of or priority to as identified in theconcurrently filed Application Data Sheet is incorporated by referenceherein in its entirety and for all purposes.

FIELD

The disclosed embodiments relate generally to bus bars for opticallyswitchable devices, and more particularly to angled bus bars for thinfilm optically switchable devices.

BACKGROUND

Various optically switchable devices are available for controllingtinting, reflectivity, etc., of window panes or lites. Electrochromicdevices are one example of optically switchable devices. Electrochromismis a phenomenon in which a material exhibits a reversibleelectrochemically-mediated change in an optical property when placed ina different electronic state, typically by being subjected to a voltagechange. The optical property being manipulated is typically one or moreof color, transmittance, absorbance, and reflectance. One well knownelectrochromic material is tungsten oxide (WO₃). Tungsten oxide is acathodic electrochromic material in which a coloration transition,transparent to blue, occurs by electrochemical reduction.

Electrochromic materials may be incorporated into, for example, windowsfor home, commercial, and other uses. The color, transmittance,absorbance, and/or reflectance of such windows may be changed byinducing a change in the electrochromic material; i.e., electrochromicwindows are windows that can be darkened or lightened electronically. Asmall voltage applied to an electrochromic device of the window willcause it to darken; reversing the voltage causes it to lighten. Thiscapability allows for control of the amount of light that passes throughthe window, and presents an enormous opportunity for electrochromicwindows to be used not only for aesthetic purposes but also forsignificant energy-savings. With energy conservation being foremost inmodern energy policy, it is expected that growth of the electrochromicwindow industry will be robust in the coming years.

SUMMARY

Angled bus bars for thin film optically switchable devices are disclosedherein. Angled bus bars may allow for the transition of a thin filmoptically switchable device symmetrically and quickly, withoutoverdriving the thin film optically switchable device.

In one embodiment, an apparatus includes a substrate with an opticallyswitchable device disposed on a surface of the substrate. The opticallyswitchable device has a perimeter with at least one corner including afirst side, a first vertex joining the first side and a second side, andthe second side. A first bus bar is affixed to the optically switchabledevice proximate to the corner and configured to deliver current and/orvoltage for driving switching of the optically switchable device. Thefirst bus bar includes a first arm and a second arm having aconfiguration that substantially follows the shape of the first side,the first vertex, and the second side of the corner. A second bus bar isaffixed to the optically switchable device and configured to delivercurrent and/or voltage for driving switching of the optically switchabledevice. The second bus bar may be angled or not. One embodiment is anelectrochromic device including at least one angled bus bar as describedherein.

In another embodiment, a method of changing an optical state of anoptically switchable device includes applying current and/or voltage toat least one angled bus bar as described herein, which is in electricalcommunication with the optically switchable device. In one embodiment,the angled bus bar is as described above, and it is the first of two busbars in electrical communication with the optically switchable device.The optically switchable device is disposed on a surface of a substrateand has a perimeter with at least one corner including a first side, afirst vertex joining the first side and a second side, and the secondside. The first bus bar is affixed to the optically switchable deviceproximate the corner. The first bus bar includes a first arm and asecond arm having a configuration that substantially follows the shapeof the first side, the first vertex, and the second side of the corner.A second bus bar, applied to an opposing electrode of the opticallyswitchable device, may be angled or not. In response to current and/orvoltage applied to the first and the second bus bars, an optical stateof the optically switchable device changes in a substantially uniformmanner.

In another embodiment, a method of fabricating an optically switchabledevice includes fabricating the optically switchable device on a surfaceof a substrate in a single integrated vacuum deposition system. Thesubstrate is in a substantially vertical orientation in the integratedvacuum deposition system. The optically switchable device has aperimeter with at least one corner including a first side, a firstvertex joining the first side and a second side, and the second side. Afirst bus bar is formed on the optically switchable device proximate tothe corner. The first bus bar includes a first arm and a second armhaving a configuration that substantially follows the shape of the firstside, the first vertex, and the second side of the corner. The first busbar is configured to deliver current and/or voltage for drivingswitching of the optically switchable device.

In some embodiments, the method further includes forming a second busbar on the optically switchable device. The second bus bar is configuredto deliver current and/or voltage for driving switching of the opticallyswitchable device. In some embodiments, the perimeter of the opticallyswitchable device has a second corner including a third side, a secondvertex joining the third side and a fourth side, and the fourth side.The second bus bar includes a third arm and a fourth arm having aconfiguration that substantially follows the shape of the third side,the second vertex, and the fourth side of the second corner.

In another embodiment, an electrochromic lite includes a substantiallytransparent substrate with an electrochromic device thereon. Theelectrochromic device has an area bounded by four sides. Theelectrochromic lite further includes a first bus bar and a second busbar. The first bus bar is in electrical communication with a bottomtransparent conductor of the electrochromic device. The second bus baris in electrical communication with a top transparent conductor of theelectrochromic device. The first bus bar is diagonally opposed to thesecond bus bar. Each of the first and second bus bars spans diagonallyopposing vertices of the area and at least some portion of the two sidesforming each of the diagonally opposing vertices.

In some embodiments, the area of the electrochromic device is asubstantially rectangular area. The at least some portion spanned by thefirst and the second bus bars is between about 10% and about 90%,between about 10% and about 65%, or between about 35% and about 65% ofthe length of the respective sides of the substantially rectangulararea.

In some embodiments, the area of the electrochromic device is asubstantially rectangular area. Each of the first and second bus bars isL-shaped. A first arm of each of the first and second bus bars traversesa portion of a longer side of the substantially rectangular area. Asecond arm of each of the first and second bus bars traverses a portionof a shorter side, substantially orthogonal to the longer side, of thesubstantially rectangular area. The first arm is longer than the secondarm. In some embodiments, the first arm spans between about 75% andabout 90% of the longer side, and the second arm spans between about 25%and about 75% of the shorter side. In some other embodiments, thesubstantially rectangular area is square and all the arms of the firstand second bus bars are of substantially equal length.

In some embodiments, the first bus bar and the second bus bar areconfigured such that the optically switchable device switches from afirst optical state to a second optical state in about 10 minutes orless. In some embodiments, the electrochromic device is all solid stateand inorganic.

These and other features and advantages will be described in furtherdetail below, with reference to the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show schematic diagrams of electrochromic devices formed onglass substrates, i.e. electrochromic lites.

FIGS. 2A and 2B show cross-sectional schematic diagrams of theelectrochromic lites as described in relation to FIGS. 1A-C integratedinto an IGU.

FIG. 3A is a schematic cross-section of an electrochromic device.

FIG. 3B is a schematic cross-section of an electrochromic device in ableached state (or transitioning to a bleached state).

FIG. 3C is a schematic cross-section of the electrochromic device shownin FIG. 3B, but in a colored state (or transitioning to a coloredstate).

FIG. 4 is a schematic cross-section of an electrochromic device in acolored state, where the device has an interfacial region which does notcontain a distinct ion conductor layer.

FIG. 5A shows a schematic diagram of an electrochromic lite with planarbus bars.

FIGS. 5B-5D show diagrams associated with the operation of theelectrochromic lite shown in FIG. 5A.

FIG. 6A shows a schematic diagram of an electrochromic lite withcylindrical bus bars.

FIGS. 6B-6D show diagrams associated with the operation of theelectrochromic lite shown in FIG. 6A.

FIG. 7A shows a schematic diagram of an electrochromic lite withperpendicular cylindrical bus bars.

FIG. 7B shows a diagram associated with the operation of theelectrochromic lite shown in FIG. 7A.

FIG. 8A shows a schematic diagram of a square-shaped electrochromic litewith angled bus bars.

FIG. 8B shows a diagram associated with the operation of theelectrochromic lite shown in FIG. 8A.

FIG. 8C shows a schematic diagram of a rectangle-shaped electrochromiclite with angled bus bars.

FIGS. 9-11 shows schematic diagrams of electrochromic lites includingangled bus bars in different configurations.

FIG. 12A shows schematic diagrams of electrochromic lites of varyingshapes including angled bus bars in different configurations.

FIG. 12B shows schematic diagrams of angled bus bars in alternativeconfigurations.

FIG. 13 shows a flowchart depicting a method of changing an opticalstate of an optically switchable device.

FIG. 14 shows a flowchart depicting a method of fabricating an opticallyswitchable device.

FIG. 15 shows a graph including plots of the percent transmittance of anelectrochromic lite with planar bus bars and an electrochromic lite withangled bus bars.

FIG. 16A shows a graph including plots of the voltage at differentpositions on a lower conductive electrode of an electrochromic lite.

FIG. 16B shows an enlarged view of the plot from the upper left handcorner of FIG. 16A.

FIG. 17 shows a graph including plots of the current density in anelectrochromic lite with planar bus bars and an electrochromic lite withangled bus bars.

DETAILED DESCRIPTION Introduction and Overview of ElectrochromicDevices: Fabrication

It should be understood that while the disclosed embodiments focus onelectrochromic (EC) windows (also referred to as smart windows), theconcepts disclosed herein may apply to other types of switchable opticaldevices, including liquid crystal devices, suspended particle devices,and the like. For example, a liquid crystal device or a suspendedparticle device, instead of an electrochromic device, could beincorporated in any of the disclosed embodiments.

In order to orient the reader to the embodiments of angled bus barsdisclosed herein, a brief discussion of electrochromic devices isprovided. This initial discussion of electrochromic devices is providedfor context only, and the subsequently described embodiments of angledbus bars are not limited to the specific features and fabricationprocesses of this initial discussion.

A particular example of an electrochromic lite is described withreference to FIGS. 1A-1C, in order to illustrate embodiments describedherein. FIG. 1A is a cross-sectional representation (see cut X-X′ ofFIG. 1C) of an electrochromic lite, 100, which is fabricated startingwith a glass sheet, 105. FIG. 1B shows an end view (see perspective Y-Y′of FIG. 1C) of EC lite 100, and FIG. 1C shows a top-down view of EC lite100. FIG. 1A shows the electrochromic lite after fabrication on glasssheet 105, edge deleted to produce area, 140, around the perimeter ofthe lite. The electrochromic lite has also been laser scribed and busbars have been attached. The glass lite 105 has a diffusion barrier,110, and a first transparent conducting oxide (TCO), 115, on thediffusion barrier. In this example, the edge deletion process removesboth TCO 115 and diffusion barrier 110, but in other embodiments onlythe TCO is removed, leaving the diffusion barrier intact. The TCO 115 isthe first of two conductive layers used to form the electrodes of theelectrochromic device fabricated on the glass sheet. In this example,the glass sheet includes underlying glass and the diffusion barrierlayer. Thus, in this example, the diffusion barrier is formed, and thenthe first TCO, an EC stack, 125, (e.g., having electrochromic, ionconductor, and counter electrode layers), and a second TCO, 130, areformed. In one embodiment, the electrochromic device (EC stack andsecond TCO) is fabricated in an integrated deposition system where theglass sheet does not leave the integrated deposition system at any timeduring fabrication of the stack. In one embodiment, the first TCO layeris also formed using the integrated deposition system where the glasssheet does not leave the integrated deposition system during depositionof the EC stack and the (second) TCO layer. In one embodiment, all ofthe layers (diffusion barrier, first TCO, EC stack, and second TCO) aredeposited in the integrated deposition system where the glass sheet doesnot leave the integrated deposition system during deposition. In thisexample, prior to deposition of EC stack 125, an isolation trench, 120,is cut through TCO 115 and diffusion barrier 110. Trench 120 is made incontemplation of electrically isolating an area of TCO 115 that willreside under bus bar 1 after fabrication is complete (see FIG. 1A). Thisis done to avoid charge buildup and coloration of the EC device underthe bus bar, which can be undesirable.

After formation of the EC device, edge deletion processes and additionallaser scribing are performed. FIG. 1A depicts areas 140 where the devicehas been removed, in this example, from a perimeter region surroundinglaser scribe trenches, 150, 155, 160, and 165, which pass through secondTCO 130 and the EC stack, but not the first TCO 115. Laser scribetrenches 150, 155, 160, and 165 are made to isolate portions of the ECdevice, 135, 145, 170, and 175, which were potentially damaged duringedge deletion processes from the operable EC device. In one embodiment,laser scribe trenches 150, 160, and 165 pass through the first TCO toaid in isolation of the device (laser scribe trench 155 does not passthrough the first TCO, otherwise it would cut off bus bar 2's electricalcommunication with the first TCO and thus the EC stack). The laser orlasers used for the laser scribe processes are typically, but notnecessarily, pulse-type lasers, for example, diode-pumped solid statelasers. For example, the laser scribe processes can be performed using asuitable laser from IPG Photonics (of Oxford, Mass.), or from Ekspla (ofVilnius, Lithuania). Scribing can also be performed mechanically, forexample, by a diamond tipped scribe. One of ordinary skill in the artwould appreciate that the laser scribing processes can be performed atdifferent depths and/or performed in a single process whereby the lasercutting depth is varied, or not, during a continuous path around theperimeter of the EC device. In one embodiment, the edge deletion isperformed to the depth of the first TCO.

After laser scribing is complete, bus bars are attached. Non-penetratingbus bar (1) is applied to the second TCO. Non-penetrating bus bar (2) isapplied to an area where the device was not deposited (e.g., from a maskprotecting the first TCO from device deposition), in contact with thefirst TCO or, in this example, where an edge deletion process (e.g.,laser ablation using an apparatus having a XY or XYZ galvanometer) wasused to remove material down to the first TCO. In this example, both busbar 1 and bus bar 2 are non-penetrating bus bars. A penetrating bus baris one that is typically pressed into and through the EC stack to makecontact with the TCO at the bottom of the stack. A non-penetrating busbar is one that does not penetrate into the EC stack layers, but rathermakes electrical and physical contact on the surface of a conductivelayer, for example, a TCO.

The TCO layers can be electrically connected using a non-traditional busbar, for example, a bus bar fabricated with screen and lithographypatterning methods. In one embodiment, electrical communication isestablished with the device's transparent conducting layers via silkscreening (or using another patterning method) a conductive ink followedby heat curing or sintering the ink. Advantages to using the abovedescribed device configuration include simpler manufacturing, forexample, and less laser scribing than conventional techniques which usepenetrating bus bars.

After the bus bars are connected, the device is integrated into aninsulated glass unit (IGU), which includes, for example, wiring the busbars and the like. In some embodiments, one or both of the bus bars areinside the finished IGU, however in one embodiment one bus bar isoutside the seal of the IGU and one bus bar is inside the IGU. In theformer embodiment, area 140 is used to make the seal with one face ofthe spacer used to form the IGU. Thus, the wires or other connection tothe bus bars runs between the spacer and the glass. As many spacers aremade of metal, e.g., stainless steel, which is conductive, it isdesirable to take steps to avoid short circuiting due to electricalcommunication between the bus bar and connector thereto and the metalspacer.

As described above, after the bus bars are connected, the electrochromiclite is integrated into an IGU, which includes, for example, wiring forthe bus bars and the like. In the embodiments described herein, both ofthe bus bars are inside the primary seal of the finished IGU. FIG. 2Ashows a cross-sectional schematic diagram of the electrochromic windowas described in relation to FIGS. 1A-C integrated into an IGU, 200. Aspacer, 205, is used to separate the electrochromic lite from a secondlite, 210. Second lite 210 in IGU 200 is a non-electrochromic lite,however, the embodiments disclosed herein are not so limited. Forexample, lite 210 can have an electrochromic device thereon and/or oneor more coatings such as low-E coatings and the like. Lite 201 can alsobe laminated glass, such as depicted in FIG. 2B (lite 201 is laminatedto reinforcing pane, 230, via resin, 235). Between spacer 205 and thefirst TCO layer of the electrochromic lite is a primary seal material,215. This primary seal material is also between spacer 205 and secondglass lite 210. Around the perimeter of spacer 205 is a secondary seal,220. Bus bar wiring/leads traverse the seals for connection to acontroller. Secondary seal 220 may be much thicker that depicted. Theseseals aid in keeping moisture out of an interior space, 225, of the IGU.They also serve to prevent argon or other gas in the interior of the IGUfrom escaping.

Introduction and Overview of Electrochromic Devices: Function

FIG. 3A schematically depicts an electrochromic device, 300, incross-section. Electrochromic device 300 includes a substrate, 302, afirst conductive layer (CL), 304, an electrochromic layer (EC), 306, anion conducting layer (IC), 308, a counter electrode layer (CE), 310, anda second conductive layer (CL), 314. Layers 304, 306, 308, 310, and 314are collectively referred to as an electrochromic stack 320. A voltagesource 316 operable to apply an electric potential across electrochromicstack 320 effects the transition of the electrochromic device from, forexample, a bleached state to a colored state (depicted). The order oflayers can be reversed with respect to the substrate.

Electrochromic devices having distinct layers as described can befabricated as all solid state and/or all inorganic devices with lowdefectivity. Such devices and methods of fabricating them are describedin more detail in U.S. patent application Ser. No. 12/645,111, entitled,“Fabrication of Low-Defectivity Electrochromic Devices,” filed on Dec.22, 2009 and naming Mark Kozlowski et al. as inventors, and in U.S.patent application Ser. No. 12/645,159, entitled, “ElectrochromicDevices,” filed on Dec. 22, 2009 and naming Zhongchun Wang et al. asinventors, both of which are incorporated by reference herein for allpurposes. It should be understood, however, that any one or more of thelayers in the stack may contain some amount of organic material. Thesame can be said for liquids that may be present in one or more layersin small amounts. It should also be understood that solid state materialmay be deposited or otherwise formed by processes employing liquidcomponents such as certain processes employing sol-gels or chemicalvapor deposition.

Additionally, it should be understood that the reference to a transitionbetween a bleached state and colored state is non-limiting and suggestsonly one example, among many, of an electrochromic transition that maybe implemented. Unless otherwise specified herein (including theforegoing discussion), whenever reference is made to a bleached-coloredtransition, the corresponding device or process encompasses otheroptical state transitions such as non-reflective-reflective,transparent-opaque, etc. Further, the term “bleached” refers to anoptically neutral state, for example, uncolored, transparent, ortranslucent. Still further, unless specified otherwise herein, the“color” of an electrochromic transition is not limited to any particularwavelength or range of wavelengths. As understood by those of skill inthe art, the choice of appropriate electrochromic and counter electrodematerials governs the relevant optical transition.

In embodiments described herein, the electrochromic device reversiblycycles between a bleached state and a colored state. In some cases, whenthe device is in a bleached state, a potential is applied to theelectrochromic stack 320 such that available ions in the stack resideprimarily in the counter electrode 310. When the potential on theelectrochromic stack is reversed, the ions are transported across theion conducting layer 308 to the electrochromic material 306 and causethe material to transition to the colored state.

Referring again to FIG. 3A, voltage source 316 may be configured tooperate in conjunction with radiant and other environmental sensors. Asdescribed herein, voltage source 316 interfaces with a device controller(not shown in this figure). Additionally, voltage source 316 mayinterface with an energy management system that controls theelectrochromic device according to various criteria such as the time ofyear, time of day, and measured environmental conditions. Such an energymanagement system, in conjunction with large area electrochromic devices(e.g., an electrochromic window), can dramatically lower the energyconsumption of a building.

Any material having suitable optical, electrical, thermal, andmechanical properties may be used as substrate 302. Such substratesinclude, for example, glass, plastic, and mirror materials. Suitableglasses include either clear or tinted soda lime glass, including sodalime float glass. The glass may be tempered or untempered.

In many cases, the substrate is a glass pane sized for residentialwindow applications. The size of such glass pane can vary widelydepending on the specific needs of the residence. In other cases, thesubstrate is architectural glass. Architectural glass is typically usedin commercial buildings, but may also be used in residential buildings,and typically, though not necessarily, separates an indoor environmentfrom an outdoor environment. In certain embodiments, architectural glassis at least 20 inches by 20 inches, and can be much larger, for example,as large as about 80 inches by 120 inches. Architectural glass istypically at least about 2 mm thick, typically between about 3 mm andabout 6 mm thick. Of course, electrochromic devices are scalable tosubstrates smaller or larger than architectural glass. Further, theelectrochromic device may be provided on a mirror of any size and shape.

On top of substrate 302 is conductive layer 304. In certain embodiments,one or both of the conductive layers 304 and 314 is inorganic and/orsolid. Conductive layers 304 and 314 may be made from a number ofdifferent materials, including conductive oxides, thin metalliccoatings, conductive metal nitrides, and composite conductors.Typically, conductive layers 304 and 314 are transparent at least in therange of wavelengths where electrochromism is exhibited by theelectrochromic layer. Transparent conductive oxides include metal oxidesand metal oxides doped with one or more metals. Examples of such metaloxides and doped metal oxides include indium oxide, indium tin oxide,doped indium oxide, tin oxide, doped tin oxide, zinc oxide, aluminumzinc oxide, doped zinc oxide, ruthenium oxide, doped ruthenium oxide andthe like. Since oxides are often used for these layers, they aresometimes referred to as “transparent conductive oxide” (TCO) layers.Thin metallic coatings that are substantially transparent may also beused.

The function of the conductive layers is to spread an electric potentialprovided by voltage source 316 over surfaces of the electrochromic stack320 to interior regions of the stack, with relatively little ohmicpotential drop. The electric potential is transferred to the conductivelayers though electrical connections to the conductive layers. In someembodiments, bus bars, one in contact with conductive layer 304 and onein contact with conductive layer 314, provide the electric connectionbetween the voltage source 316 and the conductive layers 304 and 314.The conductive layers 304 and 314 may also be connected to the voltagesource 316 with other conventional means.

Overlaying conductive layer 304 is electrochromic layer 306. In someembodiments, electrochromic layer 306 is inorganic and/or solid. Theelectrochromic layer may contain any one or more of a number ofdifferent electrochromic materials, including metal oxides. Such metaloxides include tungsten oxide (WO₃), molybdenum oxide (MoO₃), niobiumoxide (Nb₂O₅), titanium oxide (TiO₂), copper oxide (CuO), iridium oxide(Ir₂O₃), chromium oxide (Cr₂O₃), manganese oxide (Mn₂O₃), vanadium oxide(V₂O₅), nickel oxide (Ni₂O₃), cobalt oxide (Co₂O₃) and the like. Duringoperation, electrochromic layer 306 transfers ions to and receives ionsfrom counter electrode layer 310 to cause optical transitions.

Generally, the colorization (or change in any optical property—e.g.,absorbance, reflectance, and transmittance) of the electrochromicmaterial is caused by reversible ion insertion into the material (e.g.,intercalation) and a corresponding injection of a charge balancingelectron. Typically some fraction of the ions responsible for theoptical transition is irreversibly bound up in the electrochromicmaterial. Some or all of the irreversibly bound ions are used tocompensate “blind charge” in the material. In most electrochromicmaterials, suitable ions include lithium ions (Li⁺) and hydrogen ions(H⁺) (that is, protons). In some cases, however, other ions will besuitable. In various embodiments, lithium ions are used to produce theelectrochromic phenomena. Intercalation of lithium ions into tungstenoxide (WO_(3-y) (0<y≤˜0.3)) causes the tungsten oxide to change fromtransparent (bleached state) to blue (colored state).

Referring again to FIG. 3A, in electrochromic stack 320, ion conductinglayer 308 is sandwiched between electrochromic layer 306 and counterelectrode layer 310. In some embodiments, counter electrode layer 310 isinorganic and/or solid. The counter electrode layer may comprise one ormore of a number of different materials that serve as a reservoir ofions when the electrochromic device is in the bleached state. During anelectrochromic transition initiated by, for example, application of anappropriate electric potential, the counter electrode layer transferssome or all of the ions it holds to the electrochromic layer, changingthe electrochromic layer to the colored state. Concurrently, in the caseof NiWO, the counter electrode layer colors with the loss of ions.

In some embodiments, suitable materials for the counter electrodecomplementary to WO₃ include nickel oxide (NiO), nickel tungsten oxide(NiWO), nickel vanadium oxide, nickel chromium oxide, nickel aluminumoxide, nickel manganese oxide, nickel magnesium oxide, chromium oxide(Cr₂O₃), manganese oxide (MnO₂), and Prussian blue.

When charge is removed from a counter electrode 310 made of nickeltungsten oxide (that is, ions are transported from counter electrode 310to electrochromic layer 306), the counter electrode layer willtransition from a transparent state to a colored state.

In the depicted electrochromic device, between electrochromic layer 306and counter electrode layer 310, there is the ion conducting layer 308.Ion conducting layer 308 serves as a medium through which ions aretransported (in the manner of an electrolyte) when the electrochromicdevice transitions between the bleached state and the colored state.Preferably, ion conducting layer 308 is highly conductive to therelevant ions for the electrochromic and the counter electrode layers,but has sufficiently low electron conductivity that negligible electrontransfer takes place during normal operation. A thin ion conductinglayer with high ionic conductivity permits fast ion conduction and hencefast switching for high performance electrochromic devices. In certainembodiments, the ion conducting layer 308 is inorganic and/or solid.

Examples of suitable ion conducting layers (for electrochromic deviceshaving a distinct IC layer) include silicates, silicon oxides, tungstenoxides, tantalum oxides, niobium oxides, and borates. These materialsmay be doped with different dopants, including lithium. Lithium dopedsilicon oxides include lithium silicon-aluminum-oxide. In someembodiments, the ion conducting layer comprises a silicate-basedstructure. In some embodiments, a silicon-aluminum-oxide (SiAlO) is usedfor the ion conducting layer 308.

Electrochromic device 300 may include one or more additional layers (notshown), such as one or more passive layers. Passive layers used toimprove certain optical properties may be included in electrochromicdevice 300. Passive layers for providing moisture or scratch resistancemay also be included in electrochromic device 300. For example, theconductive layers may be treated with anti-reflective or protectiveoxide or nitride layers. Other passive layers may serve to hermeticallyseal electrochromic device 300.

FIG. 3B is a schematic cross-section of an electrochromic device in ableached state (or transitioning to a bleached state). In accordancewith specific embodiments, an electrochromic device, 400, includes atungsten oxide electrochromic layer (EC), 406, and a nickel-tungstenoxide counter electrode layer (CE), 410. Electrochromic device 400 alsoincludes a substrate, 402, a conductive layer (CL), 404, an ionconducting layer (IC), 408, and conductive layer (CL), 414.

A power source, 416, is configured to apply a potential and/or currentto an electrochromic stack, 420, through suitable connections (e.g., busbars) to the conductive layers, 404 and 414. In some embodiments, thevoltage source is configured to apply a potential of about 2 volts inorder to drive a transition of the device from one optical state toanother. The polarity of the potential as shown in FIG. 3A is such thatthe ions (lithium ions in this example) primarily reside (as indicatedby the dashed arrow) in nickel-tungsten oxide counter electrode layer410.

FIG. 3C is a schematic cross-section of electrochromic device 400 shownin FIG. 3B but in a colored state (or transitioning to a colored state).In FIG. 3C, the polarity of voltage source 416 is reversed, so that theelectrochromic layer is made more negative to accept additional lithiumions, and thereby transition to the colored state. As indicated by thedashed arrow, lithium ions are transported across ion conducting layer408 to tungsten oxide electrochromic layer 406. Tungsten oxideelectrochromic layer 406 is shown in the colored state. Nickel-tungstenoxide counter electrode 410 is also shown in the colored state. Asexplained, nickel-tungsten oxide becomes progressively more opaque as itgives up (deintercalates) lithium ions. In this example, there is asynergistic effect where the transition to colored states for bothlayers 406 and 410 are additive toward reducing the amount of lighttransmitted through the stack and substrate.

As described above, an electrochromic device may include anelectrochromic (EC) electrode layer and a counter electrode (CE) layerseparated by an ionically conductive (IC) layer that is highlyconductive to ions and highly resistive to electrons. As conventionallyunderstood, the ionically conductive layer therefore prevents shortingbetween the electrochromic layer and the counter electrode layer. Theionically conductive layer allows the electrochromic and counterelectrodes to hold a charge and thereby maintain their bleached orcolored states. In electrochromic devices having distinct layers, thecomponents form a stack which includes the ion conducting layersandwiched between the electrochromic electrode layer and the counterelectrode layer. The boundaries between these three stack components aredefined by abrupt changes in composition and/or microstructure. Thus,the devices have three distinct layers with two abrupt interfaces.

In accordance with certain embodiments, the counter electrode andelectrochromic electrodes are formed immediately adjacent one another,sometimes in direct contact, without separately depositing an ionicallyconducting layer. In some embodiments, electrochromic devices having aninterfacial region rather than a distinct IC layer are employed withangled bus bars described herein. Such devices, and methods offabricating them, are described in U.S. patent application Ser. Nos.12/772,055 and 12/772,075, each filed on Apr. 30, 2010, and in U.S.patent application Ser. Nos. 12/814,277 and 12/814,279, each filed onJun. 11, 2010—each of the four applications is entitled “ElectrochromicDevices,” each names Zhongchun Wang et al. as inventors, and each isincorporated by reference herein in its entirety.

FIG. 4 is a schematic cross-section of an electrochromic device, 450, ina colored state, where the device has an interfacial region, 418, whichdoes not contain a distinct IC layer. Voltage source 416, conductivelayers 414 and 404, and substrate 402 are essentially the same asdescribed in relation to FIGS. 3A-3C. Between conductive layers 414 and404 is a region 420, which includes counter electrode layer 410,electrochromic layer 406, and interfacial region 418 between them,rather than a distinct IC layer. In this example, there is no distinctboundary between counter electrode layer 410 and interfacial region 418,nor is there a distinct boundary between electrochromic layer 406 andinterfacial region 418. Rather, there is a diffuse transition between CElayer 410 and interfacial region 418, and between interfacial region 418and EC layer 406.

Transition of an Electrochromic Device

As noted above, a switchable optical device such as an electrochromicdevice reversibly cycles between two or more optical states such as ableached state and a colored state. Switching between these states iscontrolled by applying predefined current and/or voltage to the device.Higher currents and/or voltages are generally applied to largerswitchable optical devices compared to smaller switchable opticaldevices to cycle between optical states.

The speed of coloration of an electrochromic device is a function of theapplied current and/or voltage. Generally, the higher the current and/orvoltage applied across the electrochromic device, the faster theelectrochromic device will transition between optical states. Applying ahigh current and/or voltage across the electrochromic device, however,depending on the configuration of the bus bars of the electrochromicdevice, may result in damage to regions of the electrochromic device dueto the regions being exposed to too high a current and/or voltage. Theseregions are sometimes referred to as “hot spots.” On the other hand, ifa low current and/or voltage is applied across the electrochromicdevice, the device may not completely switch between optical states ormay switch at an undesirably slow rate between optical states.

Further, large electrochromic devices such as those on residentialwindows or architectural glass may exhibit an effect sometimes referredto as the “terminal effect.” This is due to the relatively high sheetresistance of thin electrochromic device films, including theelectrodes, coupled with device designs having terminals (bus bars)located outside the viewable area of the substrate, for example, only atthe edges of the device/substrate. In such devices, there is aconsiderable ohmic potential drop over the area of the device (andconcomitant leakage current), from the terminal located at the edge ofthe device to the center of the device, where there is no contact to anexternal voltage source. As a result, not only does the center region ofthe device transition more slowly than the edge regions proximateterminal contacts (which is referred to as the “curtain effect”), butthe center region may never fully transition. In other words, the centermay transition only to a limited extent in comparison to the edges.Further, to the extent that the center of the device transitions, itdoes so more slowly than the edge of the device. Yet further, it may bedifficult to hold a transition state, once such state is reached in thecenter of the device. These edge-to-center non-uniformities can beperceptible to and distracting to users.

Bus Bar Configurations

Different bus bar configurations may be used, e.g., with a largeelectrochromic device, to substantially minimize hot spots or exposingthe electrochromic device to a damaging current and/or voltage and tosubstantially minimize the curtain effect. Additionally, different busbar configurations may be used to substantially maximize the transitionrate between optical states of the electrochromic device.

FIG. 5A shows a top-down view of an electrochromic lite, 500, includingbus bars having a planar configuration. In some embodiments,electrochromic lite 500 may be similar to electrochromic lite 100 shownin FIGS. 1A-1C. Electrochromic lite 500 includes a first bus bar, 505,disposed on a first conductive layer, 510, and a second bus bar, 515,disposed on a second conductive layer, 520. An electrochromic stack (notshown) is between first conductive layer 510 and second conductive layer520. As shown, first bus bar 505 may extend substantially across oneside of first conductive layer 510. Second bus bar 515 may extendsubstantially across one side of second conductive layer 520 oppositethe side of electrochromic lite 500 on which first bus bar 505 isdisposed.

As noted above, the configuration of first and second bus bars 505 and515 in FIG. 5A may be referred to as a planar bus bar configuration.FIG. 5B is a graph showing a plot of the voltage applied to first busbar 505 and the voltage applied to second bus bar 515 that may be usedto transition electrochromic lite 500 from a bleached state to a coloredstate, for example. Plot 525 shows the voltage applied to first bus bar505 and through first conductive layer 510. As shown, the voltage dropsfrom the left hand side (e.g., where first bus bar 505 is disposed onfirst conductive layer 510 and where the voltage is applied) to theright hand side of first conductive layer 510 due to the sheetresistance of first conductive layer 510. Plot 530 shows the voltageapplied to second bus bar 515 and through second conductive layer 520.As shown, the voltage increases from the right hand side (e.g., wheresecond bus bar 515 is disposed on second conductive layer 520 and wherethe voltage is applied) to the left hand side of second conductive layer520 due to the sheet resistance of second conductive layer 520.

FIG. 5C is a graph showing a plot of the effective voltage appliedacross the electrochromic device between first and second conductivelayers 510 and 520 of electrochromic lite 500. The effective voltage isthe voltage difference between the voltage applied to first bus bar 505and through first conductive layer 510 and the voltage applied to secondbus bar 515 and through second conductive layer 520. Regions of anelectrochromic device subjected to higher effective voltages transitionbetween optical states faster than regions subjected to lower effectivevoltages. As shown, the effective voltage is the lowest at the center ofelectrochromic lite 500 and highest at the edges of electrochromic lite500.

FIG. 5D is a graph showing plots of the percent absorption of visiblelight through electrochromic lite 500 when it is transitioning from ableached state to a colored state due to the application of the voltagesapplied to first and second bus bars 505 and 515 in FIG. 5B. Plot 540 isthe percent absorption across electrochromic lite 500 a short time afterapplication of the voltages. In plot 540 the edges of electrochromiclite 500 have transitioned faster than the center of electrochromic lite500. This is the curtain effect; coloration of electrochromic lite 500starts along the edges of electrochromic lite 500 where first and secondbus bars 505 and 515 are disposed. Plot 545 shows the percent absorptionacross electrochromic lite 500, midway through the transition from ableached state to a colored state. In plot 545, electrochromic lite 500is more colored (i.e., higher percent absorption of light), but there isstill a drop in the absorption of light at the center of electrochromiclite 500. Plot 550 is the percent absorption across electrochromic lite500 when the lite is in a fully colored state. As shown, the percentabsorption of light may not be uniform across electrochromic lite 500 inthe fully colored state due to the effective voltage drop acrosselectrochromic lite 500 (see FIG. 5C), but this may not be perceptibleto the human eye.

An advantage of planar bus bar configurations includes little risk ofoverdriving an electrochromic device. However, planar bus barconfigurations may exhibit a longer duration curtain effect and takelonger to transition an electrochromic device between optical statesthan other bus bar configurations.

FIG. 6A shows a top-down view of an electrochromic lite, 600, includingbus bars having a cylindrical configuration. Electrochromic lite 600includes first bus bars, 605 and 607, disposed on a first conductivelayer, 610, and second bus bars, 615 and 617, disposed on a secondconductive layer, 620. An electrochromic stack (not shown) is betweenfirst conductive layer 610 and second conductive layer 620. First busbars 605 and 607 extend substantially across two opposing sides of firstconductive layer 610. Second bus bars 615 and 617 extend substantiallyacross two opposing sides of second conductive layer 620. As shown,first bus bars 605 and 607 and second bus bars 615 and 617 may be atlocations such that first bus bar 605 and second bus bar 615 are closeto one another and first bus bar 607 and second bus bar 617 are close toone another.

As noted above, the configuration of first bus bars 605 and 607 andsecond bus bars 615 and 617 may be referred to as a cylindrical bus barconfiguration. FIG. 6B is a graph showing a plot of the voltage appliedto first bus bars 605 and 607 and the voltage applied to second bus bars615 and 617 that may be used to transition electrochromic lite 600 froma bleached state to a colored state, for example. The same voltage maybe applied to both of the first bus bars 605 and 607 (i.e., first busbars 605 and 607 may be connected in parallel). The same voltage may beapplied to both of the second bus bars 615 and 617 (i.e., second busbars 615 and 617 may be connected in parallel). Plot 625 shows thevoltage applied to first bus bars 605 and 607 and through firstconductive layer 610. As shown, the voltage drops from the left handside (e.g., where first bus bar 605 is disposed on first conductivelayer 610 and where the voltage is applied) to the center of firstconductive layer 610 due to the sheet resistance of first conductivelayer 610. The voltage increases from the center of first conductivelayer 610 to the right hand side (e.g., where first bus bar 607 isdisposed on first conductive layer 610 and where the voltage isapplied).

Plot 630 shows the voltage applied to second bus bars 615 and 617 andthrough second conductive layer 620. As shown, the voltage increasesfrom the left hand side (e.g., where second bus bar 615 is disposed onsecond conductive layer 620 and where the voltage is applied) to thecenter of second conductive layer 620 due to the sheet resistance ofsecond conductive layer 620. The voltage decreases from the center ofsecond conductive layer 620 to the right hand side (e.g., where secondbus bar 617 is disposed on second conductive layer 620 and where thevoltage is applied).

FIG. 6C is a graph showing a plot of the effective voltage appliedacross the electrochromic device between first and second conductivelayers 610 and 620 of electrochromic lite 600. As shown, the effectivevoltage is the lowest at the center of electrochromic lite 600 andhighest at the edges of electrochromic lite 600; the effective voltageat the edges of electrochromic lite 600 with the cylindrical bus bars ishigher than the effective voltage at the edges of electrochromic lite500 due to bus bars 605 and 615 and bus bars 607 and 617 being close toone another. While the edges of electrochromic lite 600 may transitionbetween optical states rapidly due to this high effective voltage, thehigh effective voltage may overdrive the electrochromic device at theedges. Overdriving the device may mean that the device is damaged due tothe inability of the device's structure to handle excess voltage,current, and/or ion flow. For example, the device may delaminate and/orcease to function in areas where overdriven.

FIG. 6D is a graph showing plots of the percent absorption of visiblelight through electrochromic lite 600 when it is transitioning from ableached state to a colored state due to the application of the voltagesapplied to first bars 605 and 607 and second bus bars 615 and 617 inFIG. 6B. Plot 640 is the percent absorption across electrochromic lite600 a short time after application of the voltages. In plot 640 theedges of electrochromic lite 600 have transitioned faster than thecenter of electrochromic lite 600; the edges would transition fasterthan the edges of electrochromic lite 500. Plot 645 is the percentabsorption across electrochromic lite 600, midway through the transitionfrom a bleached state to a colored state. In plot 645, electrochromiclite 600 is more colored (i.e., higher percent absorption of light), butthere is still a drop in the absorption of light at the center ofelectrochromic lite 600. Plot 650 is the percent absorption acrosselectrochromic lite 600 when the lite is in a fully colored state. Asshown, the percent absorption of light may not be uniform acrosselectrochromic lite 600 in the fully colored state due to the effectivevoltage drop across electrochromic lite 600 (see FIG. 6C), but this maynot be perceptible to the human eye.

Advantages of cylindrical bus bar configurations include a shorterduration curtain effect and a shorter transition time of anelectrochromic compared to planar bus bar configurations. The first andsecond bus bars being close to one another, however, may cause hot spotsin the electrochromic device.

FIG. 7A shows a top-down view of an electrochromic lite, 700, includingbus bars having a perpendicular cylindrical configuration.Electrochromic lite 700 includes first bus bars, 705 and 707, disposedon a first conductive layer, 710, and second bus bars, 715 and 717,disposed on a second conductive layer, 720. An electrochromic stack (notshown) is between first conductive layer 710 and second conductive layer720. First bus bars 705 and 707 extend substantially across two opposingsides of first conductive layer 710. Second bus bars 715 and 717 extendsubstantially across two opposing sides of second conductive layer 720.As shown, first bus bars 705 and 707 and second bus bars 715 and 717 areat locations such that the first bus bars are substantiallyperpendicular to the second bus bars. To transition electrochromic lite700 between optical states, the same voltage may be applied to both offirst bus bars 705 and 707 (i.e., first bus bars 705 and 707 may beconnected in parallel). The same voltage may be applied to both ofsecond bus bars 715 and 717 (i.e., second bus bars 715 and 717 may beconnected in parallel).

FIG. 7B shows the coloration of electrochromic lite 700 at a time midwaythrough the transition from a bleached state to a colored state. Asshown in FIG. 7B, the corners of electrochromic lite 700 color first dueto high effective voltages at the corners. For example, the higheffective voltage at a corner, 730, of electrochromic lite 700 is due tofirst bus bar 707 and second bus bar 715 being close to one another atcorner 730. The center of electrochromic lite 700 is the last portion ofthe electrochromic lite to transition from the bleached state to thecolor state.

An advantage of perpendicular cylindrical bus bar configurations is thatthey may allow for more symmetric coloration (i.e., from the corners tothe center) of an electrochromic lite. However, perpendicularcylindrical bus bar configurations are prone to hot spots at the cornersof an electrochromic lite and damage the electrochromic device, becauseof the proximity of oppositely polarized bus bars at the corners of thedevice. For example, to obtain the desired coloration in the center ofan electrochromic lite, the corners may be overdriven, which increasesthe leakage current of the electrochromic device as well as thelikelihood of device damage/degradation.

Angled Bus Bars

Instead of the planar, cylindrical, or perpendicular cylindrical bus barconfigurations described above with respect to FIG. 5A-7B, an angled busbar may be included in some embodiments of electrochromic lites or otheroptically switchable devices. An angled bus bar may include two armsthat meet at an end of each of the arms, forming an angle between thetwo arms. For example, the two arms may form an L-shape or a V-shape. Insome embodiments, an electrochromic lite including at least one angledbus bar may transition between optical states faster and exhibit a moresymmetric transition between optical states. Further, an angled bus barmay be configured such that hot spots in an electrochromic device aresubstantially minimized.

FIG. 8A shows a top-down view of a square-shaped electrochromic lite,800, including angled bus bars. Electrochromic lite 800 is depicted inthe bleached state in FIG. 8A. Electrochromic lite 800 includes a firstbus bar, 805, disposed on a first conductive layer, 810, and a secondbus bar, 815, disposed on a second conductive layer, 820. Anelectrochromic stack (not shown) is between first conductive layer 810and second conductive layer 820. As shown, first conductive layer 810and second conductive layer 820 both have a perimeter with cornersincluding sides and vertices. The electrochromic stack between firstconductive layer 810 and second conductive layer 820 may also have aperimeter with corners including sides and vertices similar to firstconductive layer 810 and second conductive layer 820.

First bus bar 805 is disposed on first conductive layer 810 proximate toa corner of first conductive layer 810. First bus bar 805 include afirst arm, 806, and a second arm, 807, that substantially follow theshape of a first side, a first vertex, and a second side of a corner offirst conductive layer 810, respectively. Second bus bar 815 is disposedon second conductive layer 820 proximate to a corner of secondconductive layer 820. Second bus bar 815 includes a first arm, 816, anda second arm, 817 that substantially follow the shape of a first side, afirst vertex, and a second side of a corner of second conductive layer820, respectively. In some embodiments, a first bus bar and a second busbar may have configurations that are substantially similar. For example,in some embodiments, the arms of the first and second bus bars are ofsubstantially equal length. In some embodiments, a first bus bar and asecond bus bar may be substantially symmetric to one another.

In some embodiments, the first and the second arms of the bus bars mayspan about 10% to 90%, about 10% to 65%, or about 35% to 65% of thelength of the respective sides of the electrochromic device area. Insome embodiments, a first arm of a first bus bar has a length about 10%to 40%, about 35% to 65%, or about 60% to 90% of a length of the firstside of the electrochromic device. In some embodiments, the first andthe second arms of the bus bars may be substantially perpendicular. Insome embodiments, each of the first and second bus bars may span sidesdefining diagonally opposing corners of the electrochromic lite.

FIG. 8B shows the coloration of electrochromic lite 800 at a time midwaythrough the transition from a bleached state to a colored state. Asshown in FIG. 8B, corners, 830 and 835, of electrochromic lite 800 wherebus bars 805 and 815 are disposed, color first. The center band ofelectrochromic lite 800, from corners, 840 and 845, is the last portionof electrochromic lite 800 to transition from the bleached state to thecolored state.

While first conductive layer 810 and second conductive layer 820 areshown as having a substantially square shape in electrochromic lite 800,the conductive layers and the electrochromic stack disposed therebetween may have any shape, including other polygons or rectangles.

FIG. 8C shows a top-down view of a rectangular electrochromic lite, 850,including angled bus bars. Electrochromic lite 850 includes a first busbar, 855, disposed on a first conductive layer, 860, and a second busbar, 865, disposed on a second conductive layer, 870. An electrochromicstack (not shown) is between first conductive layer 860 and secondconductive layer 870. First bus bar 855 is disposed on first conductivelayer 860 proximate to a corner of first conductive layer 860. First busbar 855 includes a first arm, 856, and a second arm, 857, whichsubstantially follow the shape of a first side, a first vertex, and asecond side of a corner of first conductive layer 860. Second bus bar865 is disposed on second conductive layer 870 proximate to a corner ofsecond conductive layer 870. Second bus bar 865 includes a first arm,866, and a second arm, 867, which substantially follow the shape of afirst side, a first vertex, and a second side of a corner of secondconductive layer 870. First and second bus bars 855 and 865 are disposedon diagonally opposing corners of electrochromic lite 850. In someembodiments, a first bus bar and a second bus bar may haveconfigurations that are substantially similar.

In some embodiments, second arm 857 and 867 of each of first and secondbus bars 855 and 865, respectively, traverse a portion of a longer sideof electrochromic lite 850. First arms 856 and 866 of each of first andsecond bus bars 855 and 865, respectively, traverse a portion of ashorter side of electrochromic lite 850. In some embodiments, the firstarms and the second arms of first and second bus bars 855 and 865 aresubstantially orthogonal to one another. In some embodiments, first arms856 and 866 span about 25% to 75% of the shorter side. In someembodiments, second arms 857 and 867 span about 75% to 90% of the longerside.

In some embodiments, including at least one angled bus bar in anelectrochromic lite, as in electrochromic lites 800 and 850 describedabove with respect to FIGS. 8A and 8C, may allow for semi-symmetriccoloration (i.e., from two corners to the center) of an electrochromiclite. When transitioning from a bleached state to a colored state, allsides of the electrochromic lite may begin to color at similar rates(i.e., side preference coloration may be substantially eliminated),which reduces the asymmetry of the curtain effect. Further, the hotspots generated by, for example, perpendicular cylindrical bus barconfigurations are avoided in angled bus bar configurations. Further,the transition between optical states may occur more rapidly with angledbus bar configurations than with planar bus bar configurations withoutoverdriving regions of the electrochromic lite, as with some cylindricalor perpendicular cylindrical bus bar configurations. FIGS. 9-12B showtop-down views of electrochromic lites including angled bus bars indifferent configurations.

Referring to FIG. 9 , an electrochromic lite, 900, includes first busbars, 930 and 935, disposed on a first conductive layer, 910, and secondbus bars, 940 and 945, disposed on a second conductive layer, 920. Anelectrochromic stack (not shown) is between first conductive layer 910and second conductive layer 920. As shown, the first conductive layer910 and the second conductive layer 920 both have a perimeter withcorners including sides and vertices. The electrochromic stack betweenfirst conductive layer 910 and second conductive layer 920 may also havea perimeter with corners including sides and vertices similar to firstconductive layer 910 and second conductive layer 920.

First bus bar 930 is disposed on first conductive layer 910 proximate toa corner of first conductive layer 910. First bus bar 935 is disposed onfirst conductive layer 910 proximate to a corner of first conductivelayer 910 diagonally opposed to first bus bar 930. Similarly, second busbar 940 is disposed on second conductive layer 920 proximate to a cornerof second conductive layer 920. Second bus bar 945 is disposed on secondconductive layer 920 proximate to a corner of second conductive layer920 diagonally opposed to second bus bar 940. To transitionelectrochromic lite 900 between optical states, the same voltage may beapplied to both of first bus bars 930 and 935 (i.e., first bus bars 930and 935 may be connected in parallel). The same voltage may be appliedto both of second bus bars 940 and 945 (i.e., second bus bars 940 and945 may be connected in parallel).

Each of the bus bars includes arms that follow the shapes of the sidesand the vertex of the corner with which the bus bar is associated. Armsof first bus bars 930 and 935 are not in close proximity to arms ofsecond bus bars 940 and 945 in order to avoid hot spots, in someembodiments. For example, arm, 941, of second bus bar 940 extends alongthe side of second conductive layer 920. Arm, 936, of first bus bar 935extends along the side of first conducive layer 910, with these sides offirst conductive layer 910 and second conductive layer 920 beingsubstantially parallel. In some embodiments, the ends of arms 941 and936 do not overlap with one another (e.g., as the bus bars in acylindrical configuration do), and in some other embodiments, the endsof arms 941 and 936 are not in close proximity to one another. Thelength of arm, 942, of second bus bar 940 and the length of arm, 932, offirst bus bar 930, may be specified in a similar manner in order toavoid hot spots.

FIG. 10 shows a top-down view of an electrochromic lite, 1000, includingangled bus bars. The bus bar configuration of electrochromic lite 1000is similar to the bar configuration of electrochromic lite 900 shown inFIG. 9 , but instead of the first bus bars being diagonally opposed toone another, each of the first bus bars is diagonally opposed to asecond bus bar. Electrochromic lite 1000 includes first bus bars, 1030and 1035, disposed on a first conductive layer, 1010, and second busbars, 1040 and 1045, disposed on a second conductive layer, 1020. Anelectrochromic stack (not shown) is between first conductive layer 1010and second conductive layer 1020. As shown, the first conductive layer1010 and the second conductive layer 1020 both have a perimeter withcorners including sides and vertices. The electrochromic stack betweenfirst conductive layer 1010 and second conductive layer 1020 may alsohave a perimeter with corners including sides and vertices similar tofirst conductive layer 1010 and second conductive layer 1020.

First bus bar 1030 is disposed on first conductive layer 1010 proximateto a corner of first conductive layer 1010. Second bus bar 1040 isdisposed on second conductive layer 1020 proximate to a corner of secondconductive layer 1020 diagonally opposed to first bus bar 1030.Similarly, first bus bar 1035 is disposed on first conductive layer 1010proximate to a corner of first conductive layer 1010. Second bus bar1045 is disposed on second conductive layer 1020 proximate to a cornerof second conductive layer 1020 diagonally opposed to first bus bar1035. To transition electrochromic lite 1000 between optical states, thesame voltage may be applied to both of first bus bars 1030 and 1035(i.e., first bus bars 1030 and 1035 may be connected in parallel). Thesame voltage may be applied to both of second bus bars 1040 and 1045(i.e., second bus bars 1040 and 1045 may be connected in parallel).

Again, similar to electrochromic lite 900, each of the bus bars ofelectrochromic lite 1000 includes arms that follow the shapes of thesides and the vertex of the corner with which the bus bar is associated.The end portion of the arms of first bus bars 1030 and 1035 are not inclose proximity to the ends of the arms of second bus bars 1040 and 1045in order to avoid hot spots, in some embodiments. For example, arm,1032, of first bus bar 1030 extends along the side of first conductivelayer 1010. Arm, 1047, of second bus bar 1045 extends along the side ofsecond conducive layer 1020. In some embodiments, the ends of arms 1032and 1047 do not overlap with one another (e.g., as the bus bars in acylindrical configuration do), and in some other embodiments, the endsof arms 1032 and 1047 are not in close proximity to one another. Thelengths of the arms of first bus bar 1035 and second bus bar 1040 may bespecified in a similar manner to avoid hot spots. In another embodiment,the bus bars depicted in FIG. 10 are arranged such that bus bar 1040 and1045, while still on the lower electrode, are diagonally opposed, andbus bars 1030 and 1035, while remaining on the upper electrode, are alsodiagonally opposed.

Arm, 1031, of first bus bar 1030 and arm, 1036, of first bus bar 1035,along the same side of first conductive layer 1010, may have lengthssuch that the electrochromic lite 1000 transitions between opticalstates in a short time period of time. The arms of second bus bars 1040and 1045 along the same side of second conductive layer 1020 also mayhave lengths such that the electrochromic device transitions betweenoptical states in a short time period of time. In some embodiments, thearms of the first bus bars may meet, forming a single C-shaped first busbar. In some embodiments, the arms of the second bus bars may meet,forming a single C-shaped second bus bar. This embodiment is shown inFIG. 11 . Electrochromic lite 1100 shown in FIG. 11 includes a first busbar, 1130, disposed on a first conductive layer, 1110, and a second busbar, 1140, disposed on a second conductive layer, 1120. Note, forexample, as described above in relation to FIG. 11 , an angled bus barmay have more than one angled feature (see bus bars 1130 and 1140, eachhaving two angles). One embodiment is an angled bus bar having two ormore angles.

The angle between the two arms of an angled bus bar may approach 180degrees and may also be smaller than 90 degrees. For the purposes ofillustration only, the embodiments above are described in terms ofrectangular electrochromic lites, however, non-rectangular shapes andother optical devices are meant to be included within the scope of thedisclosed embodiments. FIG. 12A depicts top view schematics of a numberof electrochromic lites of varying shapes and angled bus barconfigurations. For example, an electrochromic window, 1200, has atrapezoidal shape and two bus bars. A lower transparent electrodesurface, 1205, bears an angled bus bar, 1215, while an upper transparentelectrode, 1210, has another angled bus bar, 1220. In this example, busbar 1215 has an angle larger than 90 degrees, while bus bar 1220 has anacute angle, less than 90 degrees. Depending upon the shape of theelectrochromic lite, the bus bars may or may not be symmetrical or spanthe same length on each arm or have the same total length. As well, anelectrochromic lite may have a combination of angled and non-angled busbars. For example, triangular lite, 1225, has an angled bus bar, 1240,on a lower electrode 1230, and a linear bus bar, 1245, on an upperelectrode, 1235. In another example, triangular electrochromic lite,1250, has a single angled bus bar, 1265, on a lower electrode, 1255,while also having two angled bus bars, 1270, on an upper electrode,1260. The shape and orientation of the bus bars will depend on the shapeof the window, the switching and/or energy requirements of the devicethey power, and the like, e.g., in order to maximize efficient switchingand/or powering, homogeneity in transitions, and to minimize hotspots.In another example, a hexagonal electrochromic lite, 1275, has a firstangled bus bar, 1286, on a lower electrode, 1280, and a second angledbus bar, 1287, on an upper electrode, 1285. In this example, angled busbars 1286 and 1287 each have three angle features (vertices). In anotherexample, a hexagonal electrochromic lite, 1290, has six angled bus bars.On a lower electrode, 1292, there are three angled bus bars, 1296, andon an upper electrode, 1294, there are also three angled bus bars, 1298.Driving algorithms for electrochromic lites are described in more detailbelow, particularly, in relation to angled bus bars and devices havingmore than two bus bars.

Angled bus bars are described herein in terms of having at least a firstarm and a second arm joined at a vertex, e.g., as depicted and describedin relation to FIG. 12A (some examples in FIG. 12A illustrate that theremay be more vertices and arms in certain embodiments). In certainembodiments, angled bus bars do not have a physical vertex. Referring toFIG. 12B, there are configurations that are equivalent, and thereforeconsidered, angled bus bars for the purposes of this disclosure. Forexample, electrochromic device 1201 has associated bus bar arms, 1202and 1203, which are electrically connected via a wire 1204. Wire 1204could also be a thin strip of bus bar material or other suitableelectrical connector. Although there is not a physical vertex per se,this assembly is an angled bus bar because there is a virtual vertex,that is, a theoretical point in space that is an intersection of twoaxes, each axis passing through the length of each bus bar arm.Likewise, similarly situated bus bar arms electrically connected by awire, 1206, at their distal ends would also be an angled bus bar. Note,in FIG. 12B, the electrical source can be connected via the wire orother connector, or on one (or both) of the bus bar arms. In oneembodiment, if the proximal ends of two bus bar arms are: 1) at someangle relative to each other as described herein for bus bar arms havinga physical vertex, 2) within about 1 mm and about 100 mm of each other,3) in electrical communication with each other, and 4) on the sameconductive layer of a device, then they are, collectively, an angled busbar. In another embodiment, if two bus bar arms: 1) each span about 10%to 90%, about 10% to 65%, or about 35% to 65% of the length of two sidesof an electrochromic device area, 2) are at some angle relative to eachother as described herein for bus bar arms having a physical vertex, 3)are in electrical communication with each other, and 4) are on the sameconductive layer of a device, then they are, collectively, an angled busbar. For the purposes of these definitions, “electrical communicationwith each other” does not include the electrical communication via theconductive layer on which the pair of bus bar arms reside.

In certain embodiments, the bus bar arms need not be in electricalcommunication with each other. For example, in one embodiment, if twobus bar arms: 1) each span about 10% to 90%, about 10% to 65%, or about35% to 65% of the length of two sides of an electrochromic device area,2) are at some angle relative to each other as described herein for busbar arms having a physical vertex, 3) are on the same conductive layerof a device, and 4) are independently held at the same polarity, eithera negative or a positive polarity, then they are, collectively, anangled bus bar. In another embodiment, if the proximal ends of two busbar arms are: 1) at some angle relative to each other as describedherein for bus bar arms having a physical vertex, 2) within about 1 mmand about 100 mm of each other, 3) are independently held at the samepolarity, either a negative or a positive polarity, and 4) on the sameconductive layer of a device, then they are, collectively, an angled busbar. In these embodiments, is it useful, but not necessary, if thepolarity applied to each of the angled bus bar's arms is similar inmagnitude. These angled bus bars, although requiring more complex drivecircuits, will transition the electrochromic device as those having aphysical vertex or one having a virtual vertex and having the armselectrical communication with each other. The objectives of avoidinghotspots and improving optical transitions remains the same, and are metwith appropriate configurations as described herein in relation toangled bus bars having physical vertices.

In some embodiments, bus bar configurations described herein may notdevelop hot spots in an optically switchable device while transitioningthe optically switchable device between optical states. Further, the busbar configurations described herein may be modified and/or combined,depending on the application. For example, in some embodiments, anoptically switchable device may have the shape of a polygon, atrapezoid, or a shape with one region that substantially forms a cornerwith other regions having curved borders; bus bars may be disposed onthe first and second conductive layers in a manner that substantiallyminimizes hot spots, substantially minimizes the curtain effect, andquickly transitions the optically switchable device between opticalstates.

In some embodiments, the lengths of the first bus bars along the edgesof the first conductive layer and the lengths of the second bus barsalong the edges of the second conductive layer are substantiallymaximized without developing hot spots in an optically switchable devicebetween the first and second conductive layers. Substantially maximizingthe lengths of the first and the second bus bars may aid in quicklytransitioning the optically switchable device between optical states.

Generally, for fast switching between optical states of an opticallyswitchable device, the first and the second bus bars should be as closeto one another as possible, due to the inherent resistance of theconducting layers (e.g., the TCO) of the device. Having the first andthe second bus bars close to each other, however, generates hot spots inthe optically switchable device, as explained above. In someembodiments, the first and the second bus bars are configured such thatdistances between extremities of the first bus bar and portions of thesecond bus bar are substantially minimized to aid in quicklytransitioning the optically switchable device without developing hotspots. Similarly, distances between extremities of the second bar andportions of the first bus bar are substantially minimized. For example,referring to FIG. 8A, a corner, A, of first bus bar 805 is an extremityof first bus bar 805. It is a point of first bus bar 805 that isfurthest away from any part of second bus bar 815. The portions ofsecond bus bar 815 that are closest to corner A of first bus bar 805 areends, B and C, of arms 816 and 817, respectively, of second bus bar 815.Thus, to aid in quickly transitioning between optical states, thedistance between corner A of first bus bar 805 and either end B or C ofsecond bus bar 815 may be substantially minimized.

Methods of Changing Optical States

FIG. 13 shows a flowchart depicting a method of changing an opticalstate of an optically switchable device. The method 1300 shown in FIG.13 describes changing an optical state of an optically switchable devicethat may be similar to the electrochromic lite 800 shown in FIG. 8A orthe electrochromic lite 850 shown in FIG. 8C. That is, method 1300describes changing an optical state of an optically switchable devicedisposed on a surface of a substrate and having a perimeter with atleast one corner including a first side, a first vertex joining thefirst side and a second side, and the second side. Method 1300 may beused to transition any of the optically switchable devices including anangled bus bar disclosed herein.

Staring with operation 1305 of method 1300, current and/or voltage of afirst polarity is applied to a first bus bar affixed to the opticallyswitchable device proximate to the corner. The first bus bar includes afirst arm and a second arm having a configuration that substantiallyfollows the shape of the first side, the first vertex, and the secondside of the corner. For example, the first bus bar referred to inoperation 1305 could be first bus bar 805 of electrochromic lite 800shown in FIG. 8A.

At operation 1310, current and/or voltage of a second polarity isapplied to a second bus bar affixed to the optically switchable device.The second bus bar referred to in operation 1310 could be second bus bar815 of electrochromic lite 800 shown in FIG. 8A. However, as describedin operation 1310, the second bus bar could have any number of differentconfigurations, and is not necessarily an angled bus bar.

At operation 1315, in response to the current and/or voltage applied tothe first and the second bus bars, an optical state of the opticallyswitchable device switches such that the switching occurs throughout theoptically switchable device substantially uniformly. In someembodiments, having at least one angled bus bar included in an opticallyswitchable device may allow the optically switchable device totransition between optical states more uniformly than the planar,cylindrical, or perpendicular cylindrical bus bar configurationsdescribed with respect to FIGS. 5A-7B.

Having at least one angled bus bar included in an optically switchabledevice may also allow the optically switchable device to switch betweenoptical states faster than the planar, cylindrical, or perpendicularcylindrical bus bar configurations. For example, in some embodiments,switching the optical state of the optically switchable device from afirst optical state to a second optical state is performed in about 10minutes or less. Of course, the switching may depend on a number offactors, e.g., the area of the electrochromic device, the sheetresistance of the conductor layers, etc.; however, in one embodiment,the 10 minute or less switching speed applies to an optically switchabledevice having an area of between about 1 square foot (0.09 m²) and about60 square feet (5.57 m²), in another embodiment between about 6 squarefeet (0.56 m²) and about 30 square feet (2.79 m²), and in yet anotherembodiment, between about 10 square feet (0.93 m²) and about 20 squarefeet (1.86 m²). Further, having at least one angled bus bar included inan optically switchable device may allow the optically switchable deviceto switch between optical states without developing hot spots in theoptically switchable device. For example, switching the optical state ofthe optically switchable device may be performed such that the currentand/or the voltage applied across the optically switchable device doesnot damage the optically switchable device.

When more than two bus bars are configured on a device, one embodimentincludes a driving algorithm that drives successive pairs of bus bars.For example, referring to FIG. 12 , electrochromic lite 1290, a drivingalgorithm may include powering opposing pairs of bus bars 1296 and 1298,serially, e.g., in a clockwise, counter clockwise, or random manner,rather than energizing all the bus bars at simultaneously. In anotherexample, referring to FIG. 10 , bus bars on opposing corners of the ECdevice may be powered as pairs, serially, where only two bus bars areenergized at any single moment in time. Using this driving algorithm,hot spots can be further avoided, and, because only opposing singlepairs of bus bars are energized at any one time, the ends of the busbars can be closer to each other, even overlapping (i.e., runningparallel, side by side but on different electrodes) because onlyopposing pairs are energized in any single moment in time. Opposingpairs need not be used; the bus bar pairs may include adjacent bus bars,e.g., those described in relation to FIG. 10 , where the ends of the busbars are spaced appropriately to avoid hot spots.

Methods of Fabrication

FIG. 14 shows a flowchart depicting a method of fabricating an opticallyswitchable device. The method 1400 shown in FIG. 14 describes a methodof fabricating a general optically switchable device. Method 1400 may beused to fabricate any of the optically switchable devices including anangled bus bar disclosed herein. The details of forming the opticallyswitchable device would depend on the specific optical device beingfabricated, however. For example, method 1400 may be used to fabricatethe electrochromic lite 800 shown in FIG. 8A or the electrochromic lite850 shown in FIG. 8C and associated bus bars. Further details regardingthe fabrication of electrochromic devices and lites are disclosed inU.S. patent application Ser. No. 12/645,111, filed Dec. 22, 2009, U.S.patent application Ser. No. 12/645,159, filed Dec. 22, 2009, U.S. patentapplication Ser. No. 12/772,055, filed Apr. 30, 2010, U.S. patentapplication Ser. No. 12/772,075, filed Apr. 30, 2010, U.S. patentapplication Ser. No. 12/814,277, filed Jun. 11, 2010, U.S. patentapplication Ser. No. 12/814,279, filed Jun. 11, 2010, and U.S. patentapplication Ser. No. 13/166,537, filed Jun. 22, 2011, all of which areincorporated by reference herein for all purposes.

Starting at operation 1405 of method 1400, an optically switchabledevice is fabricated on a surface of a substrate in a single integratedvacuum deposition system. During the fabrication process, the substrateis in a substantially vertical orientation in the integrated vacuumdeposition system. The optically switchable device includes a perimeterwith at least one corner including a first side, a first vertex joiningthe first side and a second side, and the second side.

At operation 1410, a first bus bar is formed on the optically switchabledevice proximate to the corner. The first bus bar includes a first armand a second arm having a configuration that substantially follows theshape of the first side, the first vertex, and the second side of thecorner. The first bus bar is configured to deliver current and/orvoltage for driving switching of the optically switchable device.

At operation 1415, a second bus bar is formed on the opticallyswitchable device. The second bus bar is configured to deliver currentand/or voltage for driving switching of the optically switchable device.In some embodiments, the optically switchable device may include aperimeter with a second corner including a third side, a second vertexjoining the third side and a fourth side, and the fourth side. Thesecond bus bar may include a third arm and a fourth arm having aconfiguration that substantially follows the shape of the third side,the second vertex, and the fourth side of the second corner.

Angled Bus Bar Performance

FIGS. 15-17 show graphs including plots showing the performance ofplanar bus bars as compared to angled bus bars. FIG. 15 shows a graphincluding plots of the percent transmittance of an electrochromic litewith planar bus bars and an electrochromic lite with angled bus bars.FIG. 16A shows a graph including plots of the voltage at differentpositions on a lower conductive electrode of an electrochromic lite.FIG. 17 shows a graph including plots of the current density in anelectrochromic lite with planar bus bars and an electrochromic lite withangled bus bars.

To generate these data, a tempered 26 inch×30 inch glass lite, having asodium diffusion barrier and fluorinated tin oxide transparentconducting layer, was first coated with an all solid state and inorganicEC device, as described in U.S. patent application Ser. No. 12/772,055,filed Apr. 30, 2010, U.S. patent application Ser. No. 12/772,075, filedApr. 30, 2010, U.S. patent application Ser. No. 12/814,277, filed Jun.11, 2010, U.S. patent application Ser. No. 12/814,279, filed Jun. 11,2010, and U.S. patent application Ser. No. 13/166,537, filed Jun. 22,2011, all of which are incorporated by reference herein for allpurposes. Prior to deposition, a laser isolation scribe (L1),penetrating the fluorinated tin oxide layer, was formed along the entirelength of one of the 26″ sides of the substrate, approximately ⅝″ infrom the glass edge. After the EC device coating was deposited, twolaser scribes (L2) were formed, down to the glass, one each along the30″ sides of the lite, each scribe ⅝″ from the glass edge. Another laserscribe (L3), parallel to L1, was formed along the other 26″ sideopposite L1 and ⅝″ from glass edge. Between the L1 and the nearestparallel glass edge, an ultrasonic soldered bus bar was fabricatedapproximately the length of the edge to give a conductive path to thetop conductive layer with isolation from the bottom conductive layer dueto the L1 scribe. Similarly, a soldered bus bar was placed between theL3 and the nearest parallel glass edge to allow for a conductive path tothe bottom conductive layer with isolation from the top conductive layerdue to the L3 scribe. This yielded a 26″×30″ lite with an active area of24¾″×283/4″ and a planar bus bar configuration (two parallel bus barsrunning along opposite edges of the lite).

The device was then run through a full coloration and bleaching cycleusing a combined technique of cyclic voltammetry-chronocoulometry(CVCC). During cycling, the device was monitored near the center of theactive area (plot 1505 in FIG. 15 ) midway between the L1 and L3 scribeswith a light source/detector pair. An edge of the device was monitored(plot 1510 in FIG. 15 ) with this configuration as well. The center isthe area seen to switch slowest on an electrochromic device with theaforementioned construction. This is due to the current drop off acrossthe device due to the sheet resistance of the transparent electrodelayers. The instrumentation used for measurement was an Ocean OpticsTungsten Halogen source and ThorLabs amplified silicon detector.

The device was also probed for voltage against the voltage of the busbar connected to the lower transparent electrode, in a 9 location grid(3×3 matrix) on the active area of the device, as shown in the graphs inFIG. 16A. The 9 points making up the 3×3 matrix were: a point near thetop transparent electrode bus bar (i.e., bus bar, 1605, in FIG. 16 ), apoint midway between the bus bars, and a point near the lowertransparent electrode bus bar (i.e., bus bar, 1610, in FIG. 16A), eachof these three points taken at positions near each of the 30″ edges ofthe lite and midway between the 30″ edges of the lite. Each of thegraphs shown in FIG. 16A corresponds to one of these points; the graphsare arranged between bus bars 1605 and 1610 in the manner that thedevice was probed.

The device was driven by an Arbin BT2000 battery tester which cycled thedevice as well as monitored the auxiliary voltage signals for theoptical and voltage measurements. The parameters for the cyclingalgorithm were:

-   -   1. +4 mV/s ramp from 0V to 1V    -   2. 1V hold for 10 min    -   3. Ramp from 1V to −1.3V @−500 mV/s

4. Ramp from −1.3V to −2.5V @ −6 mV/s

5. Hold at −2.5V for 30 min

6. Ramp at +500 mV/s to 0V

7. Ramp at +4 mV/s to 2V

8. 2V hold for 10 min

9. 1V hold for 10 min

The solid lines in the plots are the results of these tests, plotted asvoltage versus time. FIG. 16B shows an enlarged view of the graph fromthe upper left hand corner of FIG. 16A (i.e., graph 1615), forreference.

Following the initial test, an additional L3 scribe was formed ½″ insideone of the L2 scribes, perpendicular to the original L3, configured sothat the bus bur electrically connected to the lower transparentconducting layer could be extended along the 30″ side, in an angledconfiguration (approximately 90 degree angle in this example, and havinga “L-shape”). This bus bar was extended with solder that extendedapproximately halfway across the 30″ edge of the lite (extension 1625 ofbus bar 1605)

The bus bar electrically connected to the top transparent conductinglayer was not extended as described above, but rather replaced by asimilar L-shaped bus bar that extended down the L1 side of the lite,just inside the old bus bar, and halfway across the 30″ side of thelite, opposite the leg of the first L-shaped bus bar and adjacent to theL2 scribe (extension 1630 of bus bar 1610). This bus bar was constructedof copper tape, as ultrasonic solder here would result in an undesirableshunt in the active area of the device. This is because this bus barresides inside the first bus bar, on the device side of the L1 isolationscribe, and therefore must not penetrate the device stack.

The device was monitored in the same manner at the same locationsdescribed in the setup above. That is, the device was run through a fullcoloration and bleaching cycle using a combined technique of CVCC.During cycling, the device was monitored near the center of the activearea (plot 1515 in FIG. 15 ) midway between the L1 and L3 scribes with alight source/detector pair. An edge of the device was monitored (plot1520 in FIG. 15 ), with this configuration as well. The device was alsoprobed for voltage against the voltage of the bus bar connected to thelower transparent electrode, in a 9 location grid (3×3 matrix) on theactive area of the device, as shown in the graphs in FIG. 16A. Thedotted lines in the graphs are the results of these tests, plotted asvoltage versus time. Again, FIG. 16B shows an enlarged view of the graphfrom the upper left hand corner (i.e., graph 1615), for reference.

The L-shaped bus bar configuration significantly improved coloration andbleaching time across the device. One common metric for characterizingswitching speed of an electrochromic device is t_(80%), or time for thedevice to reach 80% of its coloration in optical density (OD). For theplanar bus bar arrangement, the center and edge t_(80%) were 38.5minutes and 22.2 minutes, respectively. With the L-shaped bus bars, thetimes decreased to 21.5 minutes and 11.5 minutes, respectively, with thelarger percent increase occurring at the edge. Moreover, the devicerange increased and became more uniform with the improved bus barconfiguration. Center OD range increased from 1.07 to 1.26 and edge ODrange went from 1.08 to 1.35. The improved coloration can be seen in theI-V curve of the CVCC test (FIG. 15 ) which is a good proxy formeasuring switching performance. As shown in FIG. 17 , the device'sleakage current changed minimally, while the peak current increased by afactor of about 1.4; plot 1705 is the current density with the planarbus bars, and plot 1710 is the current density with the L-shaped busbars. The greater increase in peak current density signifies animprovement in ion movement and hence faster coloration. The voltageprofile (FIG. 16A) as measured across the device showed improvement inall locations. Voltages switched the device not only faster, but with alarger, more uniform range.

Although the foregoing embodiments have been described in some detail tofacilitate understanding, the described embodiments are to be consideredillustrative and not limiting. It will be apparent to one of ordinaryskill in the art that certain changes and modifications can be practicedwithin the scope of the appended claims.

What is claimed is:
 1. An apparatus comprising: a substrate; anoptically switchable device disposed on a surface of the substrate andhaving a perimeter with at least one corner including a first side, afirst vertex joining the first side and a second side, and the secondside; a first bus bar affixed to the optically switchable deviceproximate to the corner and configured to deliver current and/or voltagefor driving switching of the optically switchable device, the first busbar including a first arm and a second arm having a configuration thatsubstantially follows the shape of the first side, the first vertex, andthe second side of the corner; and a second bus bar affixed to theoptically switchable device and configured to deliver current and/orvoltage for driving switching of the optically switchable device.
 2. Theapparatus of claim 1, wherein the perimeter of the optically switchabledevice further includes a second corner including a third side, a secondvertex joining the third side and a fourth side, and the fourth side,and wherein the second bus bar is affixed to the optically switchabledevice proximate to the second corner and includes a third arm and afourth arm having a configuration that substantially follows the shapeof the third side, the second vertex, and the fourth side of the secondcorner.
 3. The apparatus of claim 2, wherein the first bus bar and thesecond bus bar have configurations that are substantially similar. 4.The apparatus of claim 1, wherein the perimeter of the opticallyswitchable device further includes a third side, and wherein the secondbus bar includes a third arm having a configuration that substantiallyfollows the shape of the third side.
 5. The apparatus of claim 1,wherein the perimeter of the optically switchable device has asubstantially rectangular shape or a substantially square shape.
 6. Theapparatus of claim 1, wherein the first arm of the first bus bar has alength about 60% to 90% of a length of the first side.
 7. The apparatusof claim 1, wherein the first arm of the first bus bar has a lengthabout 35% to 65% of a length of the first side.
 8. The apparatus ofclaim 1, wherein the first arm of the first bus bar has a length about10% to 40% of a length of the first side.
 9. The apparatus of claim 1,wherein the perimeter of the optically switchable device furtherincludes a second corner including the second side, a second vertexjoining the second side and a third side, and the third side, whereinthe first bus bar further includes a third arm, wherein the second armand the third arm have a configuration that substantially follows theshape of the second side, the second vertex, and the third side of thesecond corner.
 10. The apparatus of claim 1, wherein the first bus barand the second bus bar are configured such that the optically switchabledevice switches from a first optical state to a second optical state inabout 10 minutes or less.
 11. The apparatus of claim 1, wherein theoptically switchable device includes an electrochromic device that issolid state and inorganic.
 12. The apparatus of claim 1, wherein thefirst bus bar is configured to deliver current and/or voltage to a firstconductive layer of the optically switchable device, and wherein thesecond bus bar is configured to deliver current and/or voltage to asecond conductive layer of the optically switchable device.
 13. A methodof changing an optical state of an optically switchable device disposedon a surface of a substrate and having a perimeter with at least onecorner including a first side, a first vertex joining the first side anda second side, and the second side, the method comprising: (a) applyingcurrent and/or voltage of a first polarity to a first bus bar affixed tothe optically switchable device proximate to the corner, the first busbar including a first arm and a second arm having a configuration thatsubstantially follows the shape of the first side, the first vertex, andthe second side of the corner; (b) applying current and/or voltage of asecond polarity to a second bus bar affixed to the optically switchabledevice; and (c) in response to current and/or voltage applied to thefirst and the second bus bars, switching the optical state of theoptically switchable device such that the switching occurs throughoutthe optically switchable device substantially uniformly.
 14. The methodof claim 13, wherein switching the optical state of the opticallyswitchable device from a first optical state to a second optical stateis performed in about 10 minutes or less.
 15. The method of claim 13,wherein the optically switchable device is an electrochromic device thatis solid state and inorganic.
 16. The method of claim 15, whereinswitching the optically switchable device changes the opticallyswitchable device between a bleached state and a colored state.
 17. Themethod of claim 13, wherein switching the optical state of the opticallyswitchable device is performed such that current and/or voltage appliedacross the optically switchable device does not damage the opticallyswitchable device.
 18. A method of fabricating an optically switchabledevice, the method comprising: fabricating the optically switchabledevice on a surface of a substrate in a single integrated vacuumdeposition system, the substrate being in a substantially verticalorientation in the integrated vacuum deposition system, the opticallyswitchable device having a perimeter with at least one corner includinga first side, a first vertex joining the first side and a second side,and the second side; and forming a first bus bar on the opticallyswitchable device proximate to the corner, the first bus bar including afirst arm and a second arm having a configuration that substantiallyfollows the shape of the first side, the first vertex, and the secondside of the corner, the first bus bar being configured to delivercurrent and/or voltage for driving switching of the optically switchabledevice.
 19. The method of claim 18, further comprising: forming a secondbus bar on the optically switchable device, the second bus bar beingconfigured to deliver current and/or voltage for driving switching ofthe optically switchable device.
 20. The method of claim 19, wherein theperimeter of the optically switchable device has a second cornerincluding a third side, a second vertex joining the third side and afourth side, and the fourth side, and wherein the second bus barincludes a third arm and a fourth arm having a configuration thatsubstantially follows the shape of the third side, the second vertex,and the fourth side of the second corner.